File management

mount -t ramfs -o size=1M ramfs /tmp/mountpoint

Grep files case insensitively (i.e to match boo, Boo, BOO and all other combinations):
```
$ grep -i "boo" /etc/passwd
```
Grep all files under each directory for a string “192.168.1.5”
```
$ grep -r "192.168.1.5" /etc/
```

List all recursively in list-format and filter directories from the result:
```
ls -aRl /path/to/dir | grep "^d"
```
grep "^d" ensures directories are filtered based on a regular expression (grep being the filter tool and ^ being the RegExp for: 'begin of line').
List all recursively in list-format and filter files from the result:
```
ls -aRl /path/to/dir | grep "^-"
```
grep "^-" ensures files are filtered based on a regular expression (grep being the filter tool and ^- being the RegExp for: 'begin of line').

Change all the directories to 755 (drwxr-xr-x):

find /path/to/dir -type d -exec chmod 755 {} \;

Change all the files to 644 (-rw-r--r--):

find /path/to/dir -type f -exec chmod 644 {} \;